What do your intestines, the yeast in bread dough, and a developing frog all have in common? Among other things, they all have cells that carry out mitosis, dividing to produce more cells that are genetically identical to themselves. Why do these very different organisms and tissues all need mitosis? Intestinal cells have to be replaced as they wear out; yeast cells need to reproduce to keep their population growing; and a tadpole must make new cells as it grows bigger and more complex.

Broadly speaking, mitosis simply refers to a type of cell division in which one cell (the mother) divides to produce two new cells (the daughters) that are genetically identical to itself. However, in the context of the cell cycle, mitosis also has a narrower definition: it refers to just one part of the overall division process, the part in which the DNA of the nucleus is split into two equal sets of chromosomes.